利用组合数学中的完备差集, 对原模图提出了一种新颖的准循环低密度奇偶校验码(Quasi-Cyclic Low-Density Parity-Check, QC-LDPC)扩展方法。该方法能大幅降低编译码的复杂度, 所得到的校验矩阵中不存在四环。仿真结果表明：利用该方法构造出的P-CDS-QC-LDPC(798,399)码, 在BER为10-4时, 对比基于完备差集构造的同码率CDS-QC-LDPC(1092,546)码, 其净编码增益提高约0.24dB。在BER为10-5时, 对比基于渐近边增长(Progressive Edge-Growth, PEG)算法构造的同码率PEG-LDPC(900,450)码, 其净编码增益提高约0.15dB。

A novel method to expand the protograph was proposed by using the complete difference set of the combinational mathematics of quasi-cyclic low-density parity-check(QC-LDPC) codes. The proposed method can largely reduce the encoding/decoding complexity, and there is no 4-cycle in the constructed check matrix. Simulation results show that the net coding gain(NCG) of the P-CDS-QC-LDPC(798,399) code constructed with the proposed method is about 0.24dB higher than that of the CDS-QC-LDPC(1092,546) code with the same code rate constructed with the method based on complete difference set at the bit error rate(BER) of 10-4. And the NCG of the proposed QC-LDPC codes is about 0.15dB higher than that of the PEG-LDPC(900,450) code with the same code rate constructed by the classic construction method based on the progressive edge-growth(PEG) at the BER of 10-5.